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Control Mechanism(a) of the Leptin Surge in Neonatal Appetite Regulation of Sheep PDF
By:Ashely M. Smith
Published on 2016 by

Human epidemiological studies and the use of relevant animal models have provided insight to the widely accepted concept that maternal nutrition during pregnancy is a critical factor influencing fetal growth and development. Maternal undernutrition and overnutrition/obesity have been shown to induce adverse health outcomes in offspring, including appetite dysregulation. Appetite regulation is primarily controlled by the adipocyte-derived protein hormone leptin, where a surge release of this hormone in neonatal life establishes appetite control centers within the hypothalamus. Briefly, we have reported that lambs born to ewes fed only to requirements exhibit a leptin surge within the first two weeks of postnatal life. Whereas, lambs born to overfed/obese ewes do not exhibit a neonatal leptin surge and experience appetite dysregulation in postnatal life, as evidence by offspring hyperphagia, and increased adiposity and weight gain. However, the physiological factors controlling the elimination of this leptin surge remain uncertain. Due to the known impacts of cortisol on adipose tissue differentiation and function, and the hypercortisolemia exhibited by mid- to late-gestation fetuses and newborn lambs of obese ewes, cortisol is speculated to eliminate the leptin surge in these lambs. Thus, Study 1 was conducted to determine if cortisol administration to newborn lambs born to control fed ewes would eliminate the neonatal leptin surge. Two groups of lambs received either a high or low dose of exogenous cortisol, while the third served as controls. The low dose was calculated based on lamb blood volume and was estimated to raise cortisol concentrations up to those exhibited by lambs born to obese ewes. The high dose was incorporated to ensure cortisol concentrations would be elevated sufficiently to eliminate the leptin surge, if this was the mechanism. Within two hours post-treatment, the high dose of exogenous cortisol elevated lamb plasma cortisol to concentrations observed in lambs born to obese ewes. Lambs who received the high dose exhibited a decrease in plasma leptin concentrations throughout the first ten days of postnatal life and failed to exhibit the neonatal leptin surge. Study 2 was designed to confirm observations from Study 1, using an increased sample size. However, due to an array of potential factors, including but not limited to, age, gravidity, and environment the control-fed ewes of Study 2 exhibited a reduction in body weight from early- to mid-gestation, subjecting the ewes and developing offspring to nutrient restriction. This nutrient restriction is speculated to account for the elevated fetal plasma cortisol concentrations exhibited by lambs at birth. Newborn lambs were randomly assigned to either the control group, or a cortisol treatment group, which received the same high dose of exogenous cortisol used in Study 1. However, fetal exposure to elevated cortisol is hypothesized to have induced a tissue-specific biological response in utero, therefore eliminating the leptin surge in control lambs and preventing a postnatal treatment response in cortisol treated lambs, as evidenced by similar plasma leptin concentrations between control and cortisol treated lambs. Thus, results from Study 1 and 2, coupled with data from our maternal obesity models, show that exposure to elevated cortisol in utero and early neonatal life is associated with an elimination of the lamb neonatal leptin surge.

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Book ID of Control Mechanism(a) of the Leptin Surge in Neonatal Appetite Regulation of Sheep's Books is hj1otAEACAAJ, Book which was written byAshely M. Smithhave ETAG "TMPPfN6EK7E"

Book which was published by since 2016 have ISBNs, ISBN 13 Code is 9780355134025 and ISBN 10 Code is 0355134020

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Download Control Mechanism(a) of the Leptin Surge in Neonatal Appetite Regulation of Sheep PDF Free

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